Progesterone-induced neuroprotection

Androgen effects on mesoprefrontal dopamine systems in the adult male brain

Epidemiological data show that males are more often and/or more severely affected by symptoms of prefrontal cortical dysfunction in schizophrenia, Parkinson's disease and other disorders in which dopamine circuits associated with the prefrontal cortex are dysregulated. This review focuses on research showing that these dopamine circuits are powerfully regulated by androgens. It begins with a brief overview of the sex differences that distinguish prefrontal function in health and prefrontal dysfunction or decline in aging and/or neuropsychiatric disease. This review article then spotlights data from human subjects and animal models that specifically identify androgens as potent modulators of prefrontal cortical operations and of closely related, functionally critical measures of prefrontal dopamine level or tone. Candidate mechanisms by which androgens dynamically control mesoprefrontal dopamine systems and impact prefrontal states of hypo- and hyper-dopaminergia in aging and disease are then considered. This is followed by discussion of a working model that identifies a key locus for androgen modulation of mesoprefrontal dopamine systems as residing within the prefrontal cortex itself. The last sections of this review critically consider the ways in which the organization and regulation of mesoprefrontal dopamine circuits differ in the adult male and female brain, and highlights gaps where more research is needed.

Catalpol attenuates polycystic ovarian syndrome by regulating sirtuin 1 mediated NF-κB signaling pathway

Oxidative stress plays a central role in polycystic ovary syndrome (PCOS). Catalpol (CAT) is the active ingredient of Rehmannia glutinosa Libosch which has therapeutic effect on PCOS. However, little is known about the mechanism of CAT in PCOS. PCOS rats were induced by subcutaneous injection of dehydroepiandrosteronec for four weeks and then were treated with CAT (50 mg/kg) or carboxyl methyl cellulose (the solvent of CAT) or normal saline for another 4 weeks. Histopathological observation of ovarian tissues, the levels of testosterone, estradiol and progesterone in rat plasma samples, the oxidative stress related-indexes and the expressions of NF-κB pathway-related proteins were determined. KGN cell (human ovarian granulosa cell line) was used as PCOS cell model and was transfected with siSIRT1 in the presence of CAT. The viability, proliferation and apoptosis of cells and the levels of SIRT1 and NF-κB pathway-related proteins were measured. CAT lessened the anthropometric indices and improved ovarian damage in PCOS model rats, and reduced the levels of testosterone, estradiol, progesterone and MDA, increased GSH content, and elevated the activities of catalase, GSH-Px and SOD in ovarian tissues of PCOS model rats. CAT up-regulated SIRT1 level and inhibited the activation of NF-κB signaling pathway in PCOS rat model and KGN cells. Silencing SIRT1 increased the viability and proliferation, whilst decreased the apoptosis of CAT-treated KGN cells. Silencing SIRT1 counteracted the effect of CAT on the level of oxidative stress-related factors and NF-κB signaling pathway in KGN cells. CAT attenuated PCOS by regulating SIRT1 mediated NF-κB signaling pathway.

The Role of Progestogens in Menopausal Hormone Therapy

Progestogens are steroid compounds that have the ability to induce secretory transformation in the endometrium and are utilized in menopausal hormone therapy to prevent endometrial hyperplasia and endometrial cancer. Progestogens can be derived from 21-carbon or 19-carbon steroid cytoskeletons and thus have different properties and metabolic effects beyond the progestational effects on the endometrium. This limited review will focus on the available progestogens utilized in combination hormone therapy including progesterone, medroxyprogesterone acetate, norethindrone, norethindrone acetate, levonorgestrel, and drospirenone. The impact of progestogens on a variety of target tissues including the endometrium, breast, cardiovascular system, brain, and bone, will be reviewed. Last, the current clinical regimens that can be utilized by clinicians will be discussed.

Performance characteristics of the light-initiated chemiluminescent assay for quantitative determination of progesterone

Background

To study the performance of quantitative determination of progesterone by light-initiated chemiluminescent assay (LICA).

Methods

Clinical samples of serum were used for detection of progesterone by LICA. The precision study was performed according to Clinical and Laboratory Standards Institute (CLSI) EP15-A3, the linear range validation was performed according to CLSI EP06-A, accuracy was evaluated according to CLSI EP9-A3, and the performance of detection capability was confirmed according to CLSI EP17-A2. All data were analyzed using SPSS software. Function regression analysis was performed by OriginPro software.

Results

The LICA-800 system exhibited low coefficients of variation (CVs) and high reproducibility, and the calculated synthetic CV was 2.16%. The access progesterone assay showed excellent linearity in the assay measuring range (0.37–40 ng/mL) using the polynomial regression method in accordance with CLSI EP06-A. Bias assessment was used to verify accuracy, and the percentage deviation met the quality requirements of the laboratory’s allowable deviation of 10.00%. In terms of the detection capability of LICA, the calculated limit of blank (LoB) was 0.046 ng/mL, limit of detection (LoD) was 0.057 ng/mL, and the limit of quantitation (LoQ) value was 0.161 ng/mL.

Conclusions

The competitive LICA provided a highly sensitive, accurate and precise method for measuring serum progesterone level.

A Lifecourse Perspective on Female Sex-Specific Risk Factors for Later Life Cognition

PURPOSE OF REVIEW

The prevalence of Alzheimer's disease and related dementias is greater in women compared to men. We provide a review of female sex-specific risk factors across the lifecourse for cognition in older adulthood, highlighting areas that need further study.

RECENT FINDINGS

Pregnancy may affect late-life cognition, with adverse pregnancy outcomes associated with an increased risk of cognitive decline but parity providing a protective effect. Cumulative estrogen exposure, influenced by age of menarche, menopause, and exogenous estrogen use, may modify a woman's risk for dementia. Menopause transition-associated symptoms may impact cognitive health at the time of the symptoms, but long-term effects remain unknown. As compared to natural menopause, surgical menopause seems to increase the risk for cognitive impairment. Studies that have assessed the association between women's reproductive health and cognition have produced conflicting results. Future studies that address these inconsistencies among diverse populations are needed to better care for women throughout their lives.

Why the Hips Remain Stable When the Spine Strays: A Deeper Analysis of the Relationship Between Hip Displacement and Severe Scoliosis in Patients With Cerebral Palsy

BACKGROUND

Many patients with spastic quadriplegic cerebral palsy (CP) and severe scoliosis develop hip displacement, whereas others do not. We investigated demographic characteristics, risk factors for CP, and imaging findings associated with nondisplaced hips in patients with CP and severe scoliosis.

METHODS

We retrospectively analyzed records of 229 patients with spastic quadriplegic CP and severe scoliosis who presented for treatment at our US academic tertiary care hospital between August 2005 and September 2015. Demographic characteristics, risk factors for CP, and brain magnetic resonance imaging (MRI) findings were documented. Patients were classified as Gross Motor Function Classification System (GMFCS) level 4 or higher, with 58% at GMFCS level 5.3. Displaced hips (n=181 patients) were defined as a migration percentage of ≥30% or previous surgery for hip displacement/adductor contractures. Patients who did not meet these criteria were classified as nondisplaced (n=48 patients). We used univariate analysis and multivariate logistic regression to determine associations between patient factors and hip displacement (alpha=0.05).

RESULTS

Patients born at term (≥37 wk) had 2.5 times the odds [95% confidence interval (CI): 1.3-5.0] of having nondisplaced hips compared with patients born prematurely. Females had 2.0 times the odds (95% CI: 1.0-3.9) of having nondisplaced hips compared with males. Patients with normal brain MRI findings had 9.6 times the odds (95% CI: 2.3-41) of having nondisplaced hips compared with patients with abnormal findings. Hip displacement was not associated with race (P>0.05).

CONCLUSIONS

Gestational age 37 weeks or above, female sex, and normal brain MRI findings are independently associated with nondisplaced hips in patients with spastic quadriplegic CP and severe scoliosis. These findings direct attention to characteristics that may place patients at greater risk of displacement. Future work may influence preventative screening practices and improve patient counseling regarding the risk of hip displacement.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

Dopamine-induced interactions of female mouse hypothalamic proteins with progestin receptor-A in the absence of hormone

Neural progestin receptors (PR) function in reproduction, neural development, neuroprotection, learning, memory and the anxiety response. In the absence of progestins, PR can be activated by dopamine (DA) in the rodent hypothalamus to elicit female sexual behaviour. The present study investigated mechanisms of DA activation of PR by testing the hypothesis that proteins from DA-treated hypothalami interact with PR in the absence of progestins. Ovariectomised, oestradiol-primed mice were infused with a D1-receptor agonist, SKF38393 (SKF), into the third ventricle 30 minutes prior to death. Proteins from SKF-treated hypothalami were pulled-down with glutathione S-transferase-tagged mouse PR-A or PR-B and the interactomes were analysed by mass spectrometry. The largest functional group to interact with PR-A in a DA-dependent manner was synaptic proteins. To test the hypothesis that DA activation of PR regulates synaptic proteins, we developed oestradiol-induced PR-expressing hypothalamic-like neurones derived from human-induced pluripotent stem cells (hiPSCs). Similar to progesterone (P4), SKF treatment of hiPSCs increased synapsin1/2 expression. This SKF-dependent effect was blocked by the PR antagonist RU486, suggesting that PR are necessary for this DA-induced increase. The second largest DA-dependent PR-A protein interactome comprised metabolic regulators involved in glucose metabolism, lipid synthesis and mitochondrial energy production. Interestingly, hypothalamic proteins interacted with PR-A, but not PR-B, in an SKF-dependent manner, suggesting that DA promotes the interaction of multiple hypothalamic proteins with PR-A. These in vivo and in vitro results indicate novel mechanisms by which DA can differentially activate PR isoforms in the absence of P4 and provide a better understanding of ligand-independent PR activation in reproductive, metabolic and mental health disorders in women.

Genomic sequence analyses of classical and non-classical lamprey progesterone receptor genes and the inference of homologous gene evolution in metazoans

BACKGROUND

Nuclear progesterone receptor (nPR) is an evolutionary innovation in vertebrates that mediates genomic responses to progesterone. Vertebrates also respond to progesterone via membrane progesterone receptors (mPRs) or membrane associated progesterone receptors (MAPRs) through rapid nongenomic mechanisms. Lampreys are extant agnathan vertebrates, residing at the evolutionary juncture where vertebrates diverged from invertebrates. A survey of the progesterone receptor (PR) gene sequences in lamprey genomes would inform PR gene evolutionary events during the transition from invertebrates to vertebrates.

RESULTS

In this study, we annotated sequences of one nPR, four mPR (β, γ, δ and ε) and four MAPR genes from genomes of two lamprey species (Petromyzon marinus and Lethenteron japonicum). To infer the origin and evolutionary history of PR genes, we constructed phylogenetic trees of PR homologous sequences across representative species of metazoans. Phylogenetic analyses revealed that the mPRγ gene first appeared in non-bilaterians, and the mPRβ gene likely arose from a duplication of mPRγ. On the other hand, the mPRγ gene gave rise to the mPRδ and ε genes much later in the vertebrate lineage. In addition, the mPRα gene first appeared in cartilaginous fishes, likely derived from duplication of mPRβ after the agnathan-gnathostome divergence. All known MAPR genes were present in the lamprey genomes. Progesterone receptor membrane component 1 (PGRMC1), neudesin and neuferricin genes probably evolved in parallel in non-bilaterians, whereas two copies of PGRMC genes probably derived from duplication of ancestral PGRMC1 sequence and appeared before the speciation of lampreys.

CONCLUSIONS

Non-classical mPR and MAPR genes first evolved in non-bilaterians and classical nPR genes evolved later in basal vertebrates. Sequence repertoires for membrane progesterone receptor genes in vertebrates likely originated from an ancestral metazoan sequence and expanded via several duplication events.

Female reproduction bears no survival cost in captivity for gray mouse lemurs

The survival cost of reproduction has been revealed in many free-ranging vertebrates. However, recent studies on captive populations failed to detect this cost. Theoretically, this lack of survival/reproduction trade-off is expected when resources are not limiting, but these studies may have failed to detect the cost, as they may not have fully accounted for potential confounding effects, in particular interindividual heterogeneity. Here, we investigated the effects of current and past reproductive effort on later survival in captive females of a small primate, the gray mouse lemur. Survival analyses showed no cost of reproduction in females; and the pattern was even in the opposite direction: the higher the reproductive effort, the higher the chances of survival until the next reproductive event. These conclusions hold even while accounting for interindividual heterogeneity. In agreement with aforementioned studies on captive vertebrates, these results remind us that reproduction is expected to be traded against body maintenance and the survival prospect only when resources are so limiting that they induce an allocation trade-off. Thus, the cost of reproduction has a major extrinsic component driven by environmental conditions.

Reproductive period and risk of dementia in a diverse cohort of health care members

OBJECTIVE

Women have >50% greater lifetime risk of dementia than men but the role of female-specific endocrine milieu is not well-understood. This study evaluates associations between indicators of estrogen exposure from women's reproductive period and dementia risk in a large diverse population.

METHODS

We evaluated 15,754 female members (29.9% nonwhite) of Kaiser Permanente with clinical examinations and health survey data from 1964 to 1973 and were members as of January 1, 1996. In midlife (mean age 51.1 years), women reported age at menarche and menopause and hysterectomy status. Reproductive span was calculated as menopause age minus menarche age. Dementia diagnoses were abstracted from January 1, 1996 to September 30, 2017 medical records (mean age at start of dementia follow-up 76.5 years). Cox proportional hazard models evaluated associations between aspects of reproductive span and dementia risk adjusting for demographics and life course health indicators.

RESULTS

Forty-two percent of women developed dementia. Compared to menarche at age 13.0 (mean menarche age), menarche at ≥16 was associated with 23% greater dementia risk (adjusted hazard ratio [HR] 1.23; 95% confidence interval [CI] 1.01-1.50) adjusting for demographics and life course health indicators. Natural menopause at age <47.4 (mean menopause age) was associated with 19% elevated dementia risk (HR 1.19; 95% CI 1.07-1.31). Reproductive spans <34.4 years (mean duration) were associated with 20% elevated dementia risk (HR 1.20; 95% CI 1.08-1.32). Hysterectomies were associated with 8% elevated dementia risk (HR 1.08; 95% CI 1.01-1.16).

CONCLUSION

In this large prospective cohort study, endocrine events signaling less estradiol exposure (i.e., later age at menarche, younger age at menopause, shorter reproductive span, and hysterectomies) were associated with elevated risk of dementia.

Development of a novel progesterone analog in the treatment of traumatic brain injury

Although systemic progesterone (PROG) treatment has been shown to be neuroprotective by many laboratories and in multiple animal models of brain injury including traumatic brain injury (TBI), PROG's poor aqueous solubility limits its potential for use as a therapeutic agent. The problem of solubility presents challenges for an acute intervention for neural injury, when getting a neuroprotectant to the brain quickly is crucial. Native PROG (nPROG) is hydrophobic and does not readily dissolve in an aqueous-based medium, so this makes it harder to give under emergency field conditions. An agent with properties similar to those of PROG but easier to store, transport, formulate, and administer early in emergency trauma situations could lead to better and more consistent clinical outcomes following TBI. At the same time, the engineering of a new molecule designed to treat a complex systemic injury must anticipate a range of translational issues including solubility and bioavailability. Here we describe the development of EIDD-1723, a novel, highly stable PROG analog with >10⁴-fold higher aqueous solubility than that of nPROG. We think that, with further testing, EIDD-1723 could become an attractive candidate use as a field-ready treatment for TBI patients. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".

The Progestin Receptor Interactome in the Female Mouse Hypothalamus: Interactions with Synaptic Proteins Are Isoform Specific and Ligand Dependent

Progestins bind to the progestin receptor (PR) isoforms, PR-A and PR-B, in brain to influence development, female reproduction, anxiety, and stress. Hormone-activated PRs associate with multiple proteins to form functional complexes. In the present study, proteins from female mouse hypothalamus that associate with PR were isolated using affinity pull-down assays with glutathione S-transferase–tagged mouse PR-A and PR-B. Using complementary proteomics approaches, reverse phase protein array (RPPA) and mass spectrometry, we identified hypothalamic proteins that interact with PR in a ligand-dependent and isoform-specific manner and were confirmed by Western blot. Synaptic proteins, including synapsin-I and synapsin-II, interacted with agonist-bound PR isoforms, suggesting that both isoforms function in synaptic plasticity. In further support, synaptogyrin-III and synapsin-III associated with PR-A and PR-B, respectively. PR also interacted with kinases, including c-Src, mTOR, and MAPK1, confirming phosphorylation as an integral process in rapid effects of PR in the brain. Consistent with a role in transcriptional regulation, PR associated with transcription factors and coactivators in a ligand-specific and isoform-dependent manner. Interestingly, both PR isoforms associated with a key regulator of energy homeostasis, FoxO1, suggesting a novel role for PR in energy metabolism. Because many identified proteins in this PR interactome are synaptic proteins, we tested the hypothesis that progestins function in synaptic plasticity. Indeed, progesterone enhanced synaptic density, by increasing synapsin-I–positive synapses, in rat primary cortical neuronal cultures. This novel combination of RPPA and mass spectrometry allowed identification of PR action in synaptic remodeling and energy homeostasis and reveals unique roles for progestins in brain function and disease.

Exploring the potential of natural and synthetic neuroprotective steroids against neurodegenerative disorders: A literature review

Neurodegeneration is a complex process, which leads to progressive brain damage due to loss of neurons. Despite exhaustive research, the cause of neuronal loss in various degenerative disorders is not entirely understood. Neuroprotective steroids constitute an important line of attack, which could play a major role against the common mechanisms associated with various neurodegenerative disorders like Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. Natural endogenous steroids induce the neuroprotection by protecting the nerve cells from neuronal injury through multiple mechanisms, therefore the structural modifications of the endogenous steroids could be helpful in the generation of new therapeutically useful neuroprotective agents. The review article will keep the readers apprised of the detailed description of natural as well as synthetic neuroprotective steroids from the medicinal chemistry point of view, which would be helpful in drug discovery efforts aimed toward neurodegenerative diseases.

Progesterone increased β-endorphin innervation of the locus coeruleus, but ovarian steroids had no effect on noradrenergic neurodegeneration

With the decline of ovarian steroids levels at menopause, many women experience an increase in anxiety and stress sensitivity. The locus coeruleus (LC), a central source of noradrenaline (NE), is activated by stress and is inhibited by β-endorphin. Moreover, increased NE has been implicated in pathological anxiety syndromes. Hormone replacement therapy (HRT) in menopause appears to decrease anxiety and vulnerability to stress. Therefore, we questioned the effect of HRT on the inhibitory β-endorphin innervation of the LC. In addition, we found that progesterone protects serotoninergic neurons in monkeys, leading us to question whether ovarian steroids are also neuroprotective in LC neurons in monkeys. Adult Rhesus monkeys (Macaca mulatta) were ovariectomized, and either treated with Silastic capsules that contained estradiol, estradiol+progesterone, progesterone alone or that were empty (ovariectomized; control). After 1month, the LC was obtained and processed for immunohistochemistry for β-endorphin and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL). The density of β-endorphin axons was determined with image analysis using ImageJ. The TUNEL-positive neurons were counted in the entire LC. Progesterone-alone significantly increased the density of the β-endorphin axons in the LC (p<0.01). No significant differences between groups in the number of TUNEL-positive cells in the LC were found. In conclusion, we found that HRT increases the inhibitory influence of β-endorphin in the LC, which could, in turn, contribute to reduce anxiety and increase stress resilience. In addition, we did not find compelling evidence of neurodegeneration or neuroprotection by HRT in the LC of Rhesus monkeys.

Neuroprotection by Estrogen and Progesterone in Traumatic Brain Injury and Spinal Cord Injury

In recent years there has been a growing body of clinical and laboratory evidence demonstrating the neuroprotective effects of estrogen and progesterone after traumatic brain injury (TBI) and spinal cord injury (SCI). In humans, women have been shown to have a lower incidence of morbidity and mortality after TBI compared with age-matched men. Similarly, numerous laboratory studies have demonstrated that estrogen and progesterone administration is associated with a mortality reduction, improvement in neurological outcomes, and a reduction in neuronal apoptosis after TBI and SCI. Here, we review the evidence that supports hormone-related neuroprotection and discuss possible underlying mechanisms. Estrogen and progesterone-mediated neuroprotection are thought to be related to their effects on hormone receptors, signaling systems, direct antioxidant effects, effects on astrocytes and microglia, modulation of the inflammatory response, effects on cerebral blood flow and metabolism, and effects on mediating glutamate excitotoxicity. Future laboratory research is needed to better determine the mechanisms underlying the hormones' neuroprotective effects, which will allow for more clinical studies. Furthermore, large randomized clinical control trials are needed to better assess their role in human neurodegenerative conditions.

Neuroprotective effects of estrogens: the role of cholesterol

INTRODUCTION

Experimental and clinical evidence suggests that estrogens have protective effects in the brain. Nevertheless, their potential role against neurodegenerative diseases, in particular Alzheimer's disease (AD), is still a matter of debate. The identification of the seladin-1 gene (for SELective Alzheimer's Disease INdicator-1), which appeared to be significantly less expressed in brain region affected in AD, opened a new scenario in the field of neuroprotective mechanisms. Seladin-1 was found to have neuroprotective properties through its anti-apoptotic activity. In addition, it was subsequently demonstrated that seladin-1 also has enzymatic activity, because it catalyzes the conversion of desmosterol into cholesterol. Several studies have shown that an appropriate amount of membrane cholesterol plays a pivotal role to protect nerve cells against β-amyloid toxicity in AD and to counteract the synthesis of β-amyloid.

METHODS AND RESULTS

We demonstrated that the expression of seladin-1, as well as the synthesis of cell cholesterol, is stimulated by estrogens in human neuronal precursor cells. Cholesterol enriched cells became more resistant against oxidative stress and β-amyloid toxicity. We thus hypothesized that seladin-1 might be a mediator of the neuroprotective effects of estrogens. Indeed, in cells in which seladin-1 gene expression had been silenced by siRNA the protective effects of estrogens were lost. This finding indicates that seladin-1 is a crucial mediator of the neuroprotective effects of these hormones, at least in our cell model.

CONCLUSIONS

In summary, these results establish a new link between estrogens and cholesterol, which is represented by the neuroprotective factor seladin-1.

Ovarian hormones ameliorate memory impairment, cholinergic deficit, neuronal apoptosis and astrogliosis in a rat model of Alzheimer's disease

Ovarian hormones, including progesterone (P4) and 17 β-estradiol (E2), have been shown to affect memory functions; however, the underlying mechanism whereby ovarian hormone replacement therapy may decrease the risk of Alzheimer's disease (AD) is currently unclear. The present study aimed to investigate the effects of P4 and E2 on spatial and learning memory in an ovariectomized rat model of AD. β-amyloid (Aβ) or saline were stereotaxically injected into the hippocampus of the rats and, after 1 day, ovariectomy or sham operations were performed. Subsequently, the rats were treated with P4 alone, E2 alone, or a combination of P4 and E2. Treatment with E2 and/or P4 was shown to improve the learning and memory functions of the rats, as demonstrated by the Morris water maze test. In addition, treatment with E2 and P4 was associated with increased expression levels of choline acetyltransferase and 5-hydroxytryptamine receptor 2A (5-HT2A), and decreased expression levels of the glial fibrillary acidic protein in the hippocampus of the rats. Furthermore, E2 and P4 treatment significantly attenuated neuronal cell apoptosis, as demonstrated by terminal deoxynucleotidyl transferase dUTP nick end labeling assays; thus suggesting that the ovarian hormones were able to protect against Aβ-induced neuronal cell toxicity. The results of the present study suggested that the neuroprotective effects of P4 and E2 were associated with amelioration of the cholinergic deficit, suppression of apoptotic signals and astrogliosis, and upregulation of 5-HT2A expression levels. Therefore, hormone replacement therapy may be considered an effective strategy for the treatment of patients with cognitive disorders and neurodegenerative diseases.

Distinct cognitive effects of estrogen and progesterone in menopausal women

The effects of postmenopausal hormone treatment on cognitive outcomes are inconsistent in the literature. Emerging evidence suggests that cognitive effects are influenced by specific hormone formulations, and that progesterone is more likely to be associated with positive outcomes than synthetic progestin. There are very few studies of unopposed progesterone in postmenopausal women, and none that use functional neuroimaging, a sensitive measure of neurobiological function. In this study of 29 recently postmenopausal women, we used functional MRI and neuropsychological measures to separately assess the effects of estrogen or progesterone treatment on visual and verbal cognitive function. Women were randomized to receive 90 days of either estradiol or progesterone counterbalanced with placebo. After each treatment arm, women were given a battery of verbal and visual cognitive function and working memory tests, and underwent functional MRI including verbal processing and visual working memory tasks. We found that both estradiol and progesterone were associated with changes in activation patterns during verbal processing. Compared to placebo, women receiving estradiol treatment had greater activation in the left prefrontal cortex, a region associated with verbal processing and encoding. Progesterone was associated with changes in regional brain activation patterns during a visual memory task, with greater activation in the left prefrontal cortex and right hippocampus compared to placebo. Both treatments were associated with a statistically non-significant increase in number of words remembered following the verbal task performed during the fMRI scanning session, while only progesterone was associated with improved neuropsychological measures of verbal working memory compared to placebo. These results point to potential cognitive benefits of both estrogen and progesterone.

Effects of Hormone Therapy on Cognition and Mood in Recently Postmenopausal Women: Findings from the Randomized, Controlled KEEPS-Cognitive and Affective Study

BACKGROUND

Menopausal hormone therapy (MHT) reportedly increases the risk of cognitive decline in women over age 65 y. It is unknown whether similar risks exist for recently postmenopausal women, and whether MHT affects mood in younger women. The ancillary Cognitive and Affective Study (KEEPS-Cog) of the Kronos Early Estrogen Prevention Study (KEEPS) examined the effects of up to 4 y of MHT on cognition and mood in recently postmenopausal women.

METHODS AND FINDINGS

KEEPS, a randomized, double-blinded, placebo-controlled clinical trial, was conducted at nine US academic centers. Of the 727 women enrolled in KEEPS, 693 (95.3%) participated in the ancillary KEEPS-Cog, with 220 women randomized to receive 4 y of 0.45 mg/d oral conjugated equine estrogens (o-CEE) plus 200 mg/d micronized progesterone (m-P) for the first 12 d of each month, 211 women randomized to receive 50 μg/d transdermal estradiol (t-E2) plus 200 mg/d m-P for the first 12 d of each month, and 262 women randomized to receive placebo pills and patches. Primary outcomes included the Modified Mini-Mental State examination; four cognitive factors: verbal learning/memory, auditory attention/working memory, visual attention/executive function, and speeded language/mental flexibility; and a mood measure, the Profile of Mood States (POMS). MHT effects were analyzed using linear mixed-effects (LME) models, which make full use of all available data from each participant, including those with missing data. Data from those with and without full data were compared to assess for potential biases resulting from missing observations. For statistically significant results, we calculated effect sizes (ESs) to evaluate the magnitude of changes. On average, participants were 52.6 y old, and 1.4 y past their last menstrual period. By month 48, 169 (24.4%) and 158 (22.8%) of the 693 women who consented for ancillary KEEPS-Cog were lost to follow-up for cognitive assessment (3MS and cognitive factors) and mood evaluations (POMS), respectively. However, because LME models make full use all available data, including data from women with missing data, 95.5% of participants were included in the final analysis (n = 662 in cognitive analyses, and n = 661 in mood analyses). To be included in analyses, women must have provided baseline data, and data from at least one post-baseline visit. The mean length of follow-up was 2.85 y (standard deviation [SD] = 0.49) for cognitive outcomes and 2.76 (SD = 0.57) for mood outcomes. No treatment-related benefits were found on cognitive outcomes. For mood, model estimates indicated that women treated with o-CEE showed improvements in depression and anxiety symptoms over the 48 mo of treatment, compared to women on placebo. The model estimate for the depression subscale was -5.36 × 10(-2) (95% CI, -8.27 × 10(-2) to -2.44 × 10(-2); ES = 0.49, p < 0.001) and for the anxiety subscale was -3.01 × 10(-2) (95% CI, -5.09 × 10(-2) to -9.34 × 10(-3); ES = 0.26, p < 0.001). Mood outcomes for women randomized to t-E2 were similar to those for women on placebo. Importantly, the KEEPS-Cog results cannot be extrapolated to treatment longer than 4 y.

CONCLUSIONS

The KEEPS-Cog findings suggest that for recently postmenopausal women, MHT did not alter cognition as hypothesized. However, beneficial mood effects with small to medium ESs were noted with 4 y of o-CEE, but not with 4 y of t-E2. The generalizability of these findings is limited to recently postmenopausal women with low cardiovascular risk profiles.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00154180 and NCT00623311.

Nonclassical progesterone signalling molecules in the nervous system

Progesterone (P4) regulates a wide range of cognitive, neuroendocrine, neuroimmune and neuroprotective functions. Therefore, it is not surprising that this ovarian hormone acts through multiple receptors. Ever since the 1980s, studies investigating the neural effects of P4 have focused mainly on genomic and nongenomic actions of the classical progestin receptor (PGR). More recently, two groups of nonclassical P4 signalling molecules have been identified: (i) the class II progestin and adipoQ receptor (PAQR) family, which includes PAQR 5, 6, 7, 8 and 9, also called membrane progestin receptor α (mPRα; PAQR7), mPRβ (PAQR8), mPRγ (PAQR5), mPRδ (PAQR6) and mPRε (PAQR9), and (ii) the b5-like haeme/steroid-binding protein family, which includes progesterone receptor membrane component 1 (Pgrmc1), Pgrmc2, neudesin and neuferricin. In this review, we describe the structures, neuroanatomical localisation and signalling mechanisms of these molecules. We also discuss gonadotrophin-releasing hormone regulation as an example of a physiological function regulated by multiple progesterone receptors but through different mechanisms.

Progestogens used in postmenopausal hormone therapy: differences in their pharmacological properties, intracellular actions, and clinical effects

The safety of progestogens as a class has come under increased scrutiny after the publication of data from the Women's Health Initiative trial, particularly with respect to breast cancer and cardiovascular disease risk, despite the fact that only one progestogen, medroxyprogesterone acetate, was used in this study. Inconsistency in nomenclature has also caused confusion between synthetic progestogens, defined here by the term progestin, and natural progesterone. Although all progestogens by definition have progestational activity, they also have a divergent range of other properties that can translate to very different clinical effects. Endometrial protection is the primary reason for prescribing a progestogen concomitantly with postmenopausal estrogen therapy in women with a uterus, but several progestogens are known to have a range of other potentially beneficial effects, for example on the nervous and cardiovascular systems. Because women remain suspicious of the progestogen component of postmenopausal hormone therapy in the light of the Women's Health Initiative trial, practitioners should not ignore the potential benefits to their patients of some progestogens by considering them to be a single pharmacological class. There is a lack of understanding of the differences between progestins and progesterone and between individual progestins differing in their effects on the cardiovascular and nervous systems, the breast, and bone. This review elucidates the differences between the substantial number of individual progestogens employed in postmenopausal hormone therapy, including both progestins and progesterone. We conclude that these differences in chemical structure, metabolism, pharmacokinetics, affinity, potency, and efficacy via steroid receptors, intracellular action, and biological and clinical effects confirm the absence of a class effect of progestogens.

The effects of long-term treatment with estradiol and medroxyprogesterone acetate on tyrosine hydroxylase fibers and neuron number in the medial prefrontal cortex of aged female rats

Menopausal women often initiate hormone treatment to alleviate the symptoms of menopause. Research suggests that these treatments also affect cognition, and studies in young animals indicate that hormone treatment can alter several neuroanatomical measures. However, very little is known about the effects of long-term hormone treatment on the aging female brain. This study investigated the effects of hormone treatment on neuron number and tyrosine hydroxylase (TH) in the rat medial prefrontal cortex (mPFC). Female Long Evans rats were ovariectomized at middle age (12-13 months) and placed in one of four groups: no replacement (NR) (n = 12), 17β-estradiol (E(2)) (n = 12), E(2) and progesterone (n = 7), or E(2) and medroxyprogesterone acetate (MPA) (n = 10). Animals were euthanized at 20 months, and the brains were Nissl stained; a subset was immunostained for TH [NR (n = 5); E(2) (n = 6); E(2) + MPA (n = 4); E(2) + progesterone (n = 6)]. E(2) was administered through the drinking water, and progestagens were administered via pellets inserted at the nape of the neck. Neuron number and TH fiber density were quantified in the mPFC. Hormone treatment did not alter neuron number. Treatment with E(2) and MPA resulted in greater TH densities than NR in layer 1 (P < 0.05). In layers 2/3, animals receiving E(2) had greater TH densities than NR animals (P < 0.01). These results indicate that long-term hormone treatments alter dopaminergic fibers and potentially the functioning of the aging mPFC.

Progesterone increases the release of brain-derived neurotrophic factor from glia via progesterone receptor membrane component 1 (Pgrmc1)-dependent ERK5 signaling

Progesterone (P4) is cytoprotective in various experimental models, but our understanding of the mechanisms involved is still incomplete. Our laboratory has implicated brain-derived neurotrophic factor (BDNF) signaling as an important mediator of P4's protective actions. We have shown that P4 increases the expression of BDNF, an effect mediated by the classical P4 receptor (PR), and that the protective effects of P4 were abolished using inhibitors of Trk receptor signaling. In an effort to extend our understanding of the interrelationship between P4 and BDNF signaling, we determined whether P4 influenced BDNF release and examined the role of the classical PR and a putative membrane PR, progesterone receptor membrane component-1 (Pgrmc1), as mediators of this response. Given recent data from our laboratory that supported the role of ERK5 in BDNF release, we also tested whether P4-induced BDNF release was mediated by ERK5. In this study, we found that P4 and the membrane-impermeable P4 (P4-BSA) both induced BDNF release from cultured C6 glial cells and primary astrocytes. Both these cells lack the classical nuclear/intracellular PR but express high levels of membrane-associated PR, including Pgrmc1. Using RNA interference-mediated knockdown of Pgrmc1 expression, we determined that P4-induced BDNF release was dependent on the expression of Pgrmc1, although pharmacological inhibition of the PR failed to alter the effects of P4. Furthermore, the BDNF release elicited by P4 was mediated by ERK5, and not ERK1/2. Collectively, our data describe that P4 elicits an increase in BDNF release from glia via a Pgrmc1-induced ERK5 signaling mechanism and identify Pgrmc1 as a potential therapeutic target for future hormone-based drug development for the treatment of such degenerative diseases as Alzheimer's disease as well as other diseases wherein neurotrophin dysregulation is noted.

Novel actions of progesterone: what we know today and what will be the scenario in the future?

Objectives

This article is aimed to review the novel actions of progesterone, which otherwise is considered as a female reproductive hormone. The article focuses on its important physiological actions in males too and gives an overview of its novel perspectives in disorders of central and peripheral nervous system.

Key findings

Progesterone may have a potential benefit in treatment of traumatic brain injury, various neurological disorders and male related diseases like benign prostatic hypertrophy (BPH), prostate cancer and osteoporosis. Norethisterone (NETA), a progesterone derivative, decreases bone mineral loss in male castrated mice suggesting its role in osteoporosis. In the future, progesterone may find use as a male contraceptive too, but still needs confirmatory trials for safety, tolerability and acceptability. Megestrol acetate, a progesterone derivative is preferred in prostatic cancer. Further, it may find utility in nicotine addiction, traumatic brain injury (recently entered Phase III trial) and Alzheimer's disease, diabetic neuropathy and crush injuries. Studies also suggest role of progesterone in stroke, for which further clinical trials are needed. The non genomic actions of progesterone may be in part responsible for these novel actions.

Summary

Although progesterone has shown promising role in various non-hormonal benefits, further clinical studies are needed to prove its usefulness in conditions like stroke, traumatic brain injury, neuropathy and crush injury. In male related illnesses like BPH and prostatic Ca, it may prove a boon in near future. New era of hormonal male contraception may be initiated by use of progesterone along with testosterone.

Early initiation of hormone therapy in menopausal women is associated with increased hippocampal and posterior cingulate cholinergic activity

CONTEXT

The role of ovarian hormones in maintaining neuronal integrity and cognitive function is still debated. This study was undertaken to clarify the potential relationship between postmenopausal hormone use and the cholinergic system.

OBJECTIVE

We hypothesized that early initiated hormone therapy (HT) preserves the cholinergic system and that estrogen therapy (ET) would be associated with higher levels of acetylcholinesterase activity in the posterior cingulate cortex and hippocampus compared to estrogen plus progestin therapy (EPT) or no HT.

DESIGN AND SETTING

We conducted a cross-sectional study at a university teaching hospital.

PATIENTS

Fifty postmenopausal women (age, 65.2 ± 0.7 yr) with early long-term HT (n = 34; 13 ET and 21 EPT) or no HT (n = 16) participated in the study.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURE

We measured cholinergic activity (acetylcholinesterase) in the hippocampus and posterior cingulate brain regions as measured by N-[(11)C]methylpiperidin-4-yl propionate and positron emission tomography as a marker of cholinergic function.

RESULTS

Significant effects of treatment on cholinergic activity measures were obtained in the left hippocampus (F = 3.56; P = 0.04), right hippocampus (F = 3.42; P = 0.04), and posterior cingulate (F = 3.76; P = 0.03). No significant effects were observed in a cortical control region. Post hoc testing identified greater cholinergic activity in the EPT group compared to the no-HT group in the left hippocampus (P = 0.048) and posterior cingulate (P = 0.045), with a nonstatistically significant trend in the right hippocampus (P = 0.073).

CONCLUSIONS

A differential effect of postmenopausal ET and EPT on cholinergic neuronal integrity was identified in postmenopausal women. The findings are consistent with a preservation of cholinergic neuronal integrity in the EPT group.

Estrogen protection against mitochondrial toxin-induced cell death in hippocampal neurons: antagonism by progesterone

Previously we demonstrated that mitochondrial dysfunction plays a critical role in the pathogenesis of Alzheimer's disease. Further, we have shown that the neuroprotective effects of 17β-estradiol (E2) are dependent upon mitochondrial function. In the current study, we sought to identify mitochondrial sites of E2 action that mediate neuroprotection by assessing the efficacy of E2 to protect neurons against inhibitors of mitochondrial respiration which target specific complexes within the respiratory chain. Subsequently, the impact of progesterone (P4) on E2-induced prevention against mitochondrial toxins was investigated. Mitochondrial inhibitors, rotenone, 3-NPA, antimycin, KCN, and oligomycin, exhibited concentration dependent toxicity in primary hippocampal neurons. The concentration inducing 30% cell death (LD30) was selected for analyses assessing the neuroprotective efficacy of ovarian hormones (E2 and P4). Pretreatment of hippocampal neurons with E2 significantly protected against 3-NPA (7.5mM) and antimycin (125 μM) induced cell death and was moderately neuroprotective against rotenone (3 μM). E2 was ineffective against KCN and oligomycin-induced cell death. Pretreatment with P4 was without effect against these mitochondrial inhibitors. Co-administration of P4 with E2 abolished E2 induced neuroprotection against 3-NPA and antimycin. Additional metabolic analyses indicated that E2 and P4 separately increased mitochondrial respiratory capacity whereas the co-administration of E2 and P4 resulted in diminished mitochondrial respiration. These findings indicate that E2 protects against mitochondrial toxins that target complexes I, II and III whereas P4 was without effect. The data also predict that continuous combined co-administration of estrogen and progesterone common to many hormone therapy regimens is unlikely to prevent the deficits in mitochondrial function.

Oxidative Stress-Mediated Brain Dehydroepiandrosterone (DHEA) Formation in Alzheimer's Disease Diagnosis

Neurosteroids are steroids made by brain cells independently of peripheral steroidogenic sources. The biosynthesis of most neurosteroids is mediated by proteins and enzymes similar to those identified in the steroidogenic pathway of adrenal and gonadal cells. Dehydroepiandrosterone (DHEA) is a major neurosteroid identified in the brain. Over the years we have reported that, unlike other neurosteroids, DHEA biosynthesis in rat, bovine, and human brain is mediated by an oxidative stress-mediated mechanism, independent of the cytochrome P450 17α-hydroxylase/17,20-lyase (CYP17A1) enzyme activity found in the periphery. This alternative pathway is induced by pro-oxidant agents, such as Fe(2+) and β-amyloid peptide. Neurosteroids are involved in many aspects of brain function, and as such, are involved in various neuropathologies, including Alzheimer's disease (AD). AD is a progressive, yet irreversible neurodegenerative disease for which there are limited means for ante-mortem diagnosis. Using brain tissue specimens from control and AD patients, we provided evidence that DHEA is formed in the AD brain by the oxidative stress-mediated metabolism of an unidentified precursor, thus depleting levels of the precursor in the blood stream. We tested for the presence of this DHEA precursor in human serum using a Fe(2+)-based reaction and determined the amounts of DHEA formed. Fe(2+) treatment of the serum resulted in a dramatic increase in DHEA levels in control patients, whereas only a moderate or no increase was observed in AD patients. The DHEA variation after oxidation correlated with the patients' cognitive and mental status. In this review, we present the cumulative evidence for oxidative stress as a natural regulator of DHEA formation and the use of this concept to develop a blood-based diagnostic tool for neurodegenerative diseases linked to oxidative stress, such as AD.

Neuroprotective actions of neurosteroids

Neurosteroids were initially defined as steroid hormones locally synthesized within the nervous tissue. Subsequently, they were described as steroid hormone derivatives that devoid hormonal action but still affect neuronal excitability through modulation of ionotropic receptors. Neurosteroids are further subdivided into natural (produced in the brain) and synthetic. Some authors distinguish between hormonal and regular neurosteroids in the group of natural ones. The latter group, including hormone metabolites like allopregnanolone or tetrahydrodeoxycorticosterone, is devoid of hormonal activity. Both hormones and their derivatives share, however, most of the physiological functions. It is usually very difficult to distinguish the effects of hormones and their metabolites. All these substances may influence seizure phenomena and exhibit neuroprotective effects. Neuroprotection offered by steroid hormones may be realized in both genomic and non-genomic mechanisms and involve regulation of the pro- and anti-apoptotic factors expression, intracellular signaling pathways, neurotransmission, oxidative, and inflammatory processes. Since regular neurosteroids show no affinity for steroid receptors, they may act only in a non-genomic mode. Multiple studies have been conducted so far to show efficacy of neurosteroids in the treatment of the central and peripheral nervous system injury, ischemia, neurodegenerative diseases, or seizures. In this review we focused primarily on neurosteroid mechanisms of action and their role in the process of neurodegeneration. Most of the data refers to results obtained in experimental studies. However, it should be realized that knowledge about neuroactive steroids remains still incomplete and requires confirmation in clinical conditions.

The effects of estrogen and progesterone on blood glutamate levels: evidence from changes of blood glutamate levels during the menstrual cycle in women

The gonadal steroids estrogen and progesterone have been shown to have neuroprotective properties against various neurodegenerative conditions. Excessive concentrations of glutamate have been found to exert neurotoxic properties. We hypothesize that estrogen and progesterone provide neuroprotection by the autoregulation of blood and brain glutamate levels. Venous blood samples (10 ml) were taken from 31 men and 45 women to determine blood glutamate, estrogen, progesterone, glucose, glutamate-pyruvate transaminase (GPT), and glutamate-oxaloacetate transaminase (GOT) levels, collected on Days 1, 7, 12, and 21 of the female participants' menstrual cycle. Blood glutamate concentrations were higher in men than in women at the start of menstruation (P < 0.05). Blood glutamate levels in women decreased significantly on Days 7 (P < 0.01), 12 (P < 0.001), and 21 (P < 0.001) in comparison with blood glutamate levels on Day 1. There was a significant decrease in blood glutamate levels on Days 12 (P < 0.001) and 21 (P < 0.001) in comparison with blood glutamate levels on Day 7. Furthermore, there was an increase in blood glutamate levels on Day 21 compared with Day 12 (P < 0.05). In women, there were elevated levels of estrogen on Days 7 (P < 0.05), 12, and 21 (P < 0.001), and elevated levels of progesterone on Days 12 and 21 (P < 0.001). There were no differences between men and women with respect to blood glucose concentrations. Concentrations of GOT (P < 0.05) and GPT (P < 0.001) were significantly higher in men than in women during the entire cycle. The results of this study demonstrate that blood glutamate levels are inversely correlated to levels of plasma estrogen and progesterone.

Progesterone promotes the survival of newborn neurons in the dentate gyrus of adult male mice

This study investigated the effects of progesterone (P4) on the production and survival of neurons in the hippocampal dentate gyrus of adult male mice. The administration of P4 (4 mg/kg) for 3 consecutive days beginning on the 0-2nd day after the first BrdU-injection (BrdU-D(0-2)) produced an approximately twofold increase in the number of 28- and 56-day-old BrdU(+) cells in comparison to the controls, whereas it did not alter the number of 24/48-h-old BrdU(+) cells. P4 preferentially promoted the survival of newborn neurons when administered at BrdU-D(5-7), but not at BrdU-D(10-12) and BrdU-D(15-17). Androstenedione (Ad), testosterone (TE), or estradiol (E2) at the same-dose of P4, when administered at BrdU-D(0-2), could not replicate the effect of P4, while the inhibition of 5alpha-reductase by finasteride did not affect the P4-action, indicating that the P4-effect is exerted by P4 itself but not by its metabolites. On the other hand, the P4R antagonist RU486 partially suppressed the P4-effect, while inhibitors for Src, MEK, or PI3K totally suppressed the P4-effect. Finally, the P4-enhanced survival of newborn neurons was accompanied by a potentiation of spatial learning and memory, which was P4R-dependent. These findings suggest that P4 enhances the survival of newborn neurons through P4R and/or the Src-ERK and PI3K pathways independent of its influence on cell proliferation, which is well correlated with the potentiated spatial cognitive function of P4-treated animals.

The neuroprotective properties of palmitoylethanolamine against oxidative stress in a neuronal cell line

Background

N-acylethanolamines (NAEs) are lipids upregulated in response to cell and tissue injury and are involved in cytoprotection. Arachidonylethanolamide (AEA) is a well characterized NAE that is an endogenous ligand at cannabinoid and vanilloid receptors, but it exists in small quantities relative to other NAE types. The abundance of other NAE species, such as palmitoylethanolamine (PEA), together with their largely unknown function and receptors, has prompted us to examine the neuroprotective properties and mechanism of action of PEA. We hypothesized that PEA protects HT22 cells from oxidative stress and activates neuroprotective kinase signaling pathways.

Results

Indeed PEA protected HT22 cells from oxidative stress in part by mediating an increase in phosphorylated Akt (pAkt) and ERK1/2 immunoreactivity as well as pAkt nuclear translocation. These changes take place within a time frame consistent with neuroprotection. Furthermore, we determined that changes in pAkt immunoreactivity elicited by PEA were not mediated by activation of cannabinoid receptor type 2 (CB2), thus indicating a novel mechanism of action. These results establish a role for PEA as a neuroprotectant against oxidative stress, which occurs in a variety of neurodegenerative diseases.

Conclusions

The results from this study reveal that PEA protects HT22 cells from oxidative stress and alters the localization and expression levels of kinases known to be involved in neuroprotection by a novel mechanism. Overall, these results identify PEA as a neuroprotectant with potential as a possible therapeutic agent in neurodegenerative diseases involving oxidative stress.

Anterior hippocampal volume is reduced in behaviorally depressed female cynomolgus macaques

Hippocampal (HC) function and morphology have been implicated in the pathophysiology of depression. Reduced HC volume has been observed in depressed humans, although the effect is not always significant. Studies of functional differentiation of the HC have revealed that the anterior portion is associated with emotional and anxiety-related functioning, and the posterior portion with memory processing. As such, measuring whole HC volume may mask differences seen only in the anterior or posterior HC. We used unbiased stereology to measure whole, anterior, and posterior HC volumes in 12 adult female cynomolgus macaques, half of which exhibited spontaneously occurring depressive behavior defined as a slumped/collapsed body posture with open eyes, and a relative lack of responsivity to environmental stimuli. The two groups were otherwise matched on circulating estradiol, progesterone, and cortisol levels, social status, estimated age, and body weight. Frozen postmortem HC tissue from depressed and nondepressed monkeys was serially sectioned and thionin-stained. According to established neuroanatomical guidelines and with the aid of Neurolucida software (MBF Bioscience), every 10th section throughout the extent of the HC was manually traced and used to reconstruct the 3D models used to determine volumes. Anterior and posterior HC were delineated by the presence or absence of the uncus. No significant differences were found between depressed and nondepressed monkeys for whole or posterior HC volume, although the average HC volume was 4% smaller in depressed than nondepressed monkeys. Anterior HC volumes were significantly smaller (15.4%) in depressed compared to nondepressed monkeys. These results indicate that reduced volume in the anterior HC, an area previously implicated in emotional functioning, may be associated with a depressive phenotype in female cynomolgus macaques.

Oestrogen and progestins differently prevent glutamate toxicity in cortical neurons depending on prior hormonal exposure via the induction of neural nitric oxide synthase

Sex steroids are important for brain function and protection. However, growing evidence suggests that these actions might depend on the timing of exposure to steroids. We have studied the effects of steroid administration on the survival of neural cells and we have partially characterized the possible mechanisms. The effect of a 24h pre-treatment with 17beta-estradiol or 17beta-estradiol plus progesterone or medroxyprogesterone acetate on the toxic action of l-glutamate was used to test the experimental hypothesis. Pre-exposure to either steroid combinations turned in enhanced cell survival. Instead, addition of sex steroids together with l-glutamate, in the absence of a pre-exposure had no protective effect. Pre-treatment with the steroid combinations resulted in increased neural NOS expression and activity and blockade of NOS abolished the cytoprotective effects of steroids. These results suggest that NOS induction might be involved in sex steroid-induced neuroprotection. Furthermore, these data supports the hypothesis that prolonged and continued exposure to oestrogen and progesterone, leading to changes in gene expression, is necessary to obtain neuroprotection induced by sex steroids.

Neurosteroid biosynthesis: enzymatic pathways and neuroendocrine regulation by neurotransmitters and neuropeptides

Neuroactive steroids synthesized in neuronal tissue, referred to as neurosteroids, are implicated in proliferation, differentiation, activity and survival of nerve cells. Neurosteroids are also involved in the control of a number of behavioral, neuroendocrine and metabolic processes such as regulation of food intake, locomotor activity, sexual activity, aggressiveness, anxiety, depression, body temperature and blood pressure. In this article, we summarize the current knowledge regarding the existence, neuroanatomical distribution and biological activity of the enzymes responsible for the biosynthesis of neurosteroids in the brain of vertebrates, and we review the neuronal mechanisms that control the activity of these enzymes. The observation that the activity of key steroidogenic enzymes is finely tuned by various neurotransmitters and neuropeptides strongly suggests that some of the central effects of these neuromodulators may be mediated via the regulation of neurosteroid production.

ent-Steroids: novel tools for studies of signaling pathways

Membrane receptors are often modulated by steroids and it is necessary to distinguish the effects of steroids at these receptors from effects occurring at nuclear receptors. Additionally, it may also be mechanistically important to distinguish between direct effects caused by binding of steroids to membrane receptors and indirect effects on membrane receptor function caused by steroid perturbation of the membrane containing the receptor. In this regard, ent-steroids, the mirror images of naturally occurring steroids, are novel tools for distinguishing between these various actions of steroids. The review provides a background for understanding the different actions that can be expected of steroids and ent-steroids in biological systems, references for the preparation of ent-steroids, a short discussion about relevant forms of stereoisomerism and the requirements that need to be fulfilled for the interaction between two molecules to be enantioselective. The review then summarizes results of biophysical, biochemical and pharmacological studies published since 1992 in which ent-steroids have been used to investigate the actions of steroids in membranes and/or receptor-mediated signaling pathways.

Neuroprotective actions of sex steroids in Parkinson's disease

The sex difference in Parkinson's disease, with a higher susceptibility in men, suggests a modulatory effect of sex steroids in the brain. Numerous studies highlight that sex steroids have neuroprotective properties against various brain injuries. This paper reviews the protective effects of sex hormones, particularly estradiol, progesterone and androgens, in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) animal model of Parkinson's disease as compared to methamphetamine toxicity. The molecular mechanisms underlying beneficial actions of sex steroids on the brain have been investigated showing steroid, dose, timing and duration specificities and presently focus is on the dopamine signaling pathways, the next frontier. Both genomic and non-genomic actions of estrogen converge to promote survival factors and show sex differences. Neuroprotection by estrogen involves activation of signaling molecules such as the phosphatidylinositol-3 kinase/Akt and the mitogen-activated protein kinase pathways. Interaction with growth factors, such as insulin-like growth factor 1, also contributes to protective actions of estrogen.

Is progesterone a candidate neuroprotective factor for treatment following ischemic stroke?

Gender differences in stroke outcome have implicated steroid hormones as potential neuroprotective candidates. However, no clinical trials examining hormone replacement therapy on outcome following ischemic stroke have investigated the effect of progesterone-only treatment. In this review the authors examine the experimental evidence for the neuroprotective potential of progesterone and give an insight into potential mechanisms of action following ischemic stroke. To date, 17 experimental studies have investigated the neuroprotective potential of progesterone for ischemic stroke in terms of ability to both reduce cell loss and increase functional outcome. Of these 17 published studies the majority reported a beneficial effect with three studies reporting a nil effect and only one study reporting a negative effect. However, there are important issues that the authors address in this review in terms of the methodological quality of studies in relation to the STAIR recommendations. In terms of the proposed mechanisms of progesterone neuroprotection we show that progesterone is versatile and acts at multiple targets to facilitate neuronal survival and minimize cell damage and loss. A large amount of experimental evidence indicates that progesterone is a neuroprotective candidate for ischemic stroke; however, to progress to clinical trial a number of key experimental studies remain outstanding.

Increased mortality for neurological and mental diseases following early bilateral oophorectomy

BACKGROUND

The effects of oophorectomy on brain aging remain uncertain.

METHODS

We conducted a cohort study with long-term follow-up of women in Olmsted County, Minn., USA, who underwent either unilateral or bilateral oophorectomy before the onset of menopause from 1950 through 1987. Each member of the oophorectomy cohort was matched by age to a referent woman from the same population who had not undergone any oophorectomy. We studied underlying and contributory causes of death in 1,274 women with unilateral oophorectomy, 1,091 women with bilateral oophorectomy, and 2,383 referent women.

RESULTS

Mortality for neurological or mental diseases was increased in women who underwent bilateral oophorectomy before age 45 years compared with referent women (hazard ratio = 5.24; 95% confidence interval = 2.02-13.6; p < 0.001). Within this age stratum, mortality was similar in women who were or were not treated with estrogen from the time of oophorectomy through age 45 years, and in women who had bilateral oophorectomy for prophylaxis or for treatment of a benign ovarian condition. Mortality was also increased in women who underwent unilateral oophorectomy before age 45 years without concurrent hysterectomy.

CONCLUSIONS

Bilateral oophorectomy performed before age 45 years is associated with increased mortality for neurological or mental diseases.

Seizures and reproductive function: insights from female rats with epilepsy

OBJECTIVE

Chronic seizures in women can have adverse effects on reproductive function, such as polycystic ovarian syndrome, but it has been difficult to dissociate the effects of epilepsy from the role of antiepileptic drugs. To distinguish the effects of chronic seizures from medication, we used the laboratory rat, because an epileptic condition can be induced without concomitant anticonvulsant drug treatment.

METHODS

Adult female rats were administered the chemoconvulsant pilocarpine to initiate status epilepticus, which was decreased in severity by the anticonvulsant diazepam. These rats developed spontaneous seizures in the ensuing weeks, and are therefore termed epileptic. Controls were saline-treated rats, or animals that were injected with pilocarpine but did not develop status epilepticus. Ovarian cyclicity and weight gain were evaluated for 2 to 3 months. Serum hormone levels were assayed from trunk blood, which was collected at the time of death. Paraformaldehyde-fixed ovaries were evaluated quantitatively.

RESULTS

Rats that had pilocarpine-induced seizures had an increased incidence of acyclicity by the end of the study, even if status epilepticus did not occur. Ovarian cysts and weight gain were significantly greater in epileptic than control rats, whether rats maintained cyclicity or not. Serum testosterone was increased in epileptic rats, but estradiol, progesterone, and prolactin were not.

INTERPRETATIONS

The results suggest that an epileptic condition in the rat leads to increased body weight, cystic ovaries, and increased testosterone levels. Although caution is required when comparing female rats with women, the data suggest that recurrent seizures have adverse effects, independent of antiepileptic drugs.

Long-term effects of bilateral oophorectomy on brain aging: unanswered questions from the Mayo Clinic Cohort Study of Oophorectomy and Aging

In the Mayo Clinic Cohort Study of Oophorectomy and Aging, women who had both ovaries removed before reaching natural menopause experienced a long-term increased risk of parkinsonism, cognitive impairment or dementia, and depressive and anxiety symptoms. Here, we discuss five possible mechanistic interpretations of the observed associations; first, the associations may be non-causal because they result from the confounding effect of genetic variants or of other risk factors; second, the associations may be mediated by an abrupt reduction in levels of circulating estrogen; third, the associations may be mediated by an abrupt reduction in levels of circulating progesterone or testosterone; fourth, the associations may be mediated by an increased release of gonadotropins by the pituitary gland; and fifth, genetic variants may modify the hormonal effects of bilateral oophorectomy through simple or more complex interactions. Results from other studies are cited as evidence for or against each possible mechanism. These putative causal mechanisms are probably intertwined, and their clarification is a research priority.

Progesterone regulation of synaptic transmission and plasticity in rodent hippocampus

Ovarian hormones influence memory formation by eliciting changes in neural activity. The effects of various concentrations of progesterone (P4) on synaptic transmission and plasticity associated with long-term potentiation (LTP) and long-term depression (LTD) were studied using in vitro hippocampal slices. Extracellular studies show that the highest concentration of P4 tested (10(-6) M) decreased the baseline synaptic transmission and magnitude of LTP, but did not affect LTD. Intracellular studies suggest the P4 effect to be mediated, at least in part, by GABA(A) activity. These results establish a general effect of P4 on synaptic transmission, multiple forms of synaptic plasticity, and a possible mechanism of P4 action in hippocampus.

Non-genomic progesterone actions in female reproduction

BACKGROUND

The steroid hormone progesterone is indispensable for mammalian procreation by controlling key female reproductive events that range from ovulation to implantation, maintenance of pregnancy and breast development. In addition to activating the progesterone receptors (PRs)-B and -A, members of the superfamily of ligand-dependent transcription factors, progesterone also elicits a variety of rapid signalling events independently of transcriptional or genomic regulation. This review covers our current knowledge on the mechanisms and relevance of non-genomic progesterone signalling in female reproduction.

METHODS

PubMed was searched up to August 2008 for papers on progesterone actions in ovary/breast/endometrium/myometrium/brain, focusing primarily on non-genomic signalling mechanisms.

RESULTS

Convergence and intertwining of rapid non-genomic events and the slower transcriptional actions critically determine the functional response to progesterone in the female reproductive system in a cell-type- and environment-specific manner. Several putative progesterone-binding moieties have been implicated in rapid signalling events, including the 'classical' PR and its variants, progesterone receptor membrane component 1, and the novel family of membrane progestin receptors. Progesterone and its metabolites have also been implicated in the allosteric regulation of several unrelated receptors, such as gamma-aminobutyric acid type A, oxytocin and sigma(1) receptors.

CONCLUSIONS

Identification of the mechanisms and receptors that relay rapid progesterone signalling is an area of research fraught with difficulties and controversy. More in-depth characterization of the putative receptors is required before the non-genomic progesterone pathway in normal and pathological reproductive function can be targeted for pharmacological intervention.

Effects of neurosteroids on hydrogen peroxide- and staurosporine-induced damage of human neuroblastoma SH-SY5Y cells

Neurosteroids are important regulators of central nervous system function and may be involved in processes of neuronal cell survival. This study was undertaken to test the effect of dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), pregnenolone (PGL), pregnenolone sulfate (PGLS), and allopregnanolone (Allo) on hydrogen peroxide- and staurosporine-induced toxicity in SH-SY5Y cells. It has been found that DHEAS inhibited the hydrogen peroxide toxicity in a concentration-dependent manner, whereas DHEA was active only at higher doses. PGL and PGLS showed neuroprotective effects only at the lowest concentration. Allo had no significant effect on hydrogen peroxide-evoked lactate dehydrogenase release and at the highest concentration aggravated its toxic effects. Next part of this study evaluated neurosteroid effects on staurosporine-induced apoptosis. DHEAS, DHEA, and PGL significantly antagonized effects of staurosporine on both caspase-3 activity and mitochondrial membrane potential. PGLS and Allo inhibited the staurosporine-induced changes in both apoptotic parameters only at the lowest concentration. Antiapoptotic properties of neurosteroids were positively verified by Hoechst staining. Furthermore, as shown by calcein assay, DHEA, DHEAS, and PGL increased viability of staurosporine-treated cells, and these effects were attenuated by specific inhibitors of phosphatidylinositol 3-kinase (PI3-K) and extracellular signal-regulated protein kinase (ERK)-mitogen activated protein kinase (MAPK). These data indicate that neurosteroids prevent SH-SY5Y cell damage related to oxidative processes and activation of mitochondrial apoptotic pathway. Moreover, neuroprotective effects of DHEA, DHEAS seem to depend on PI3-K and ERK/MAPK signaling pathways. It can be suggested that, at physiological concentrations, all studied neurosteroids participate in the inhibition of neuronal apoptosis, but with various potencies.

Number of children is associated with neuropathology of Alzheimer's disease in women

OBJECTIVE

To examine the association between number of born children and neuropathology of Alzheimer's disease (AD).

METHODS

The brains of 86 subjects with data on the number of biological children born, were studied postmortem. Primary analyses included 73 subjects (average age at death=80; 42 women) devoid of cerebrovascular disease associated lesions (i.e., infarcts) or of non-AD related neuropathology. Women were significantly older at death than men (85.6 vs. 73.4; p<.0005) but did not differ significantly from men in number of children or dementia severity. Secondary analyses included 13 additional subjects who had concomitant cerebrovascular disease. Density of neuritic plaques (NPs) and neurofibrillary tangles (NFTs) in the hippocampus, entorhinal cortex, amygdala and multiple regions of the cerebral cortex, as well as composites of these indices reflecting overall neuropathology, were analyzed. For men and women separately, partial correlations, controlling for age at death and dementia severity, were used to assess the associations of number of children with these neuropathological variables.

RESULTS

Among women, all the partial correlations were positive, with statistical significance for overall neuropathology (r=.37; p=.02), overall NPs (r=.36; p=.02), and for NPs in the amygdala (r=.47; p=.002). Among men, none of the partial correlations were statistically significant. Results of the secondary analyses were similar.

CONCLUSIONS

Since the associations between number of children and neuropathology of AD were found for women only, they might reflect sex-specific mechanisms (such as variations in estrogen or luteinizing hormone levels) rather than social, economic, biological or other mechanisms common to both men and women.

Alcohol and estrogen replacement therapy in postmenopausal women. Direct and mediated effects on cognitive component processes

The literature remains contentious regarding the separate and combined effects of moderate drinking and estrogen replacement therapy (ERT) on cognition. In the current study, the authors sought to disentangle the predictive utility of alcohol use, ERT and their interaction on the episodic and semantic memory stores of postmenopausal women. It was predicted that relationships between moderate drinking, ERT and cognition would be attenuated by demographic and health-related factors. Postmenopausal women (n = 298) completed a battery of cognitive tests designed to assess speed and accuracy of episodic and knowledge-based cognitive processing. Potentially confounding variables were categorized and tested as mediators in hierarchical regression analyses. Moderate drinking was a weak predictor of episodic availability prior to removal of potential mediators. ERT use was a significant predictor of episodic and knowledge-based availability; no mediators were identified. Alcohol moderated ERT, as a combined alcohol/ERT variable was shown to be related to cognition. Neither moderate drinking nor ERT use was associated with cognitive speed. These findings suggest that positive relationships between alcohol and cognition are likely mediated by other variables, and should not be regarded as a benefit of drinking. Further, results support ERT as a predictor of knowledge-based and episodic availability, independent of mood stabilization or socioeconomic influences. Finally, alcohol and ERT appear to interact to impact both episodic and knowledge-based performance.

Hormone therapy effects on social behavior and activity levels of surgically postmenopausal cynomolgus monkeys

The purpose of the experiments reported here was to investigate central nervous system effects of commonly prescribed postmenopausal hormone therapies in a primate model, the cynomolgus monkey (Macaca fascicularis). The results of two experiments are reported. In the first, ovariectomized adult cynomolgus monkeys were treated for eight weeks each with oral micronized 17beta-estradiol (E2) (n=23), E2+medroxyprogesterone acetate (MPA) (n=23), E2+progesterone (P4) (n=23), and placebo (n=23) using a crossover design. In the second, ovariectomized adult cynomolgus monkeys were treated for eight weeks with oral micronized E2+oral micronized P4 (n=10), or E2+intravaginal micronized P4 delivered via a Silastic ring (n=8), or oral placebo and intravaginal placebo (n=5), using a parallel arm design. Behavior was recorded during weeks two through four. Cerebrospinal fluid (CSF) and blood were sampled, and 24h heart rate recorded by telemetry during weeks five through seven. Monoaminergic metabolites were assayed in CSF, and cortisol was assayed in serum. There were no significant effects of treatment on CSF monoaminergic metabolites or heart rate. E2+MPA increased cortisol concentrations. While there were some differences in effects between experiments, both progestogens and both routes of administration increased time spent resting, particularly resting in body contact, resulting in increased passive affiliative interaction. Thus, synthetic progestogens appear to be as sedating as progesterone, and the ring delivery system does not appear to protect the central nervous system from effects of progestogens. Further research is needed to explore social context as an important feature of behavioral response to steroid hormone regimens and to verify and extend knowledge of systemic effects of vaginal ring-delivered progestogens.